Business and consumers use a wide variety of fixed and mobile wireless terminals, including cell phones, pagers, Personal Communication Services (PCS) systems, and fixed wireless access devices (i.e., vending machine with cellular capability). Wireless service providers continually try to create new markets for wireless devices and expand existing markets by making wireless devices and services cheaper and more reliable. To attract new customers, wireless service providers implement new services, especially digital data services that, for example, enable a user to browse the Internet or send and receive e-mail.
Many of these new services are made possible by the use of smart antenna arrays that transmit data from a base station to a mobile station (i.e., downlink or forward link transmission) using beamforming techniques. Beamforming focuses a transmit beam in the direction of a selected mobile station and, therefore, uses much less power than conventional transmission techniques that broadcast the data in all directions at equal strength. Moreover, since the beam is focused towards a selected mobile station, the signal power is greatly reduced in other directions, thereby reducing signal interference in other mobile stations. Some systems attempt to maximize the antenna gain through beamforming, which can be optimal for some transmission environments.
Another approach to forward link transmission is the use of space-time coding to achieve diversity transmissions. Some systems attempt to maximize diversity gain through the use of space-time codes, which can be optimal for some transmission environments.
Therefore, there is a need in the art for an improved capability of adapting forward link transmissions to a variety of transmission environments. In particular, there is a need in the art for a method and a related apparatus that are capable of dynamically adapting between beamforming and diversity transmission in the forward link.